Add support for `site` parameter to fetch stats from different StackExchange sites

[QueenDekim]

This PR introduces support for a new query parameter site, allowing the service to fetch user statistics from any StackExchange site instead of being limited to StackOverflow.

• New site query parameter (defaults to stackoverflow if not provided).
• Handles .com suffix by stripping it automatically.
• Updated API request to api.stackexchange.com to use the chosen site.
• Updated rank URL generation to point to the correct site domain.

Why: Previously, the service only supported StackOverflow. With this change, it becomes more flexible and can be used for other StackExchange communities.

Testing:

• Call with ?userID=<id> → defaults to StackOverflow.
• Call with ?userID=<id>&site=superuser → fetches from SuperUser.
• Call with ?userID=<id>&site=askubuntu.com → .com suffix is stripped and handled correctly.

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Project	Deployment	Preview	Comments	Updated (UTC)
stackoverflow-card	Ready	Preview	Comment	Sep 10, 2025 6:16pm

[QueenDekim]

don't pay attention to the commits after closing (and before reopening the PR), there I just made the repository for myself